Generally, when a fuel amount is reduced during driving of a gasoline vehicle, an exhaust gas emission amount is reduced to meet the exhaust gas regulations. However, a risk of having adverse effects on drivability such as an engine stall and a fluctuation in an engine revolution per minute (RPM) may be increased due to fuel natures.
This is due to natures of gasoline fuel variously changed by region and season, and of formation low temperature and low volatile fuel conditions by the changed fuel natures. Particularly, the adverse effect on the low temperature drivability due to the low temperature and low volatile fuel conditions is becoming serious in a gasoline vehicle to which a gasoline direct injection (GDI) engine is applied.
As a result, after a low temperature/low volatile fuel condition control mode (or low volatile fuel condition control logic) is applied to the gasoline vehicle, and the low temperature/low volatile fuel condition control mode determines the low temperature/low volatile fuel conditions, that may come across due to regional differences and seasonal differences upon the fuel amount reduction driving, based on an engine RPM, an engine state, an elapsed starting time, and an engine coolant temperature, drivability robustness is maintained.
For example, the low temperature/low volatile fuel condition control mode is a mode that detects an excessive RPM drop phenomenon of an actual RPM relative to a targeted RPM under the low volatile fuel conditions determined upon the fuel reduction driving, performs switching to a rich lambda control to increase a fuel amount to thereby prevent the adverse effect on the drivability, on the basis of a followability evaluation result of the actual RPM relative to the targeted RPM, performs combustion mode switching from a suction single injection to a suction compression split injection, or simultaneously performs the combustion mode switching and the increase in the fuel amount.
Therefore, the low temperature/low volatile fuel condition control mode greatly contributes to the drivability robustness of a gasoline vehicle, in particular, a gasoline vehicle using a gasoline direct injection (GDI) engine, under the low temperature/low volatile fuel conditions.